Compounds of the class of π-conjugated polymers have been the subject of numerous publications in recent decades. They are also known as conductive polymers or synthetic metals.
Due to the considerable delocalisation of the π-electrons along the main chain, these polymers exhibit interesting (nonlinear) optical properties and, once oxidised or reduced, are good electrical conductors. As a consequence, these compounds may be used in various practical applications, such as for example in data storage, optical signal processing, the suppression of electromagnetic interference (EMI) and solar energy conversion, as well as in rechargeable batteries, light-emitting diodes, field effect transistors, printed circuit boards, sensors, capacitors, electrochromic devices and antistatic materials.
Examples of known π-conjugated polymers are polypyrroles, polythiophenes, polyanilines, polyacetylenes, polyphenylenes and poly(p-phenylene vinylenes). One particularly important and widely industrially used polythiophene is poly(ethylene 3,4-dioxythiophene) (Baytron®P), which, in its oxidised form, exhibits very high levels of conductivity.
However, other derivatives of poly(3,4-dioxythiophene) are also of interest, since, by suitable selection of the residues attached to the two oxygen atoms of the 3,4-dioxythiophene, it is possible purposefully to adjust, for example, the polymer's solubility in organic solvents, its electrochemical properties and its conductivity.
A problematic issue associated with the use of such poly(3,4-dioxythiophene) derivatives is that the thiophene monomers required are often only available by means of complex, low-yielding syntheses or are completely unobtainable by means of usual methods.